Cox 020 PeeWee rebuild questions

Hi Guys,
Thank you for the feedback on the reed. That makes sense. I may try polishing it a bit more on the worn side to see it will clean up any. I know I'm spending a lot of time on it when the mylar replacement reeds would be a simple answer. But since this is my first refurbishment, I'm still exploring what is possible.

My last part to clean up is the crankshaft per rdw777's instructions. I've obtained some 2000 grit wet/dry paper to use. I was going to double-back tape a piece to a popsicle-stick and mount the crankshaft in my drill press.

The friend and I that gave this little PeeWee to me are going to be bouncing off the walls wanting to see if it runs. So let me ask a couple more questions.

If once assembled, I run it a couple of times and immediately disassemble, clean all residual castor oil out and reassemble with the "air tool oil", can the gaskets be reused. Primarily the fuel tank to crankcase gasket and the head gaskets (there will be two because the fuel I obtained is 25% nitro). I remember as a kid, I would take the glow head off many times on the couple of 049s I had to check to see if it was still good when having engine start problems. I'd put it back together without any thought to replacing the head gasket. I was a kid, what did I know! The fuel tank to crankcase gasket would also come off intact and I would reuse that. So, please any comments in regard to gasket reusability would help.

Thanks,
Dave

LooseSpinner99 wrote:The fuel tank to crankcase gasket would also come off intact and I would reuse that. So, please any comments in regard to gasket reusability would help.

Dave, yes, you can reuse the gaskets if they are still in good shape. I even reuse them when say, that gasket has lost one of its ends around a screw but the tank edge is still intact. Sometimes, there could be a touch of warp on the tank to crankcase interface. In that case short of dressing the crankcase and perhaps around a screw hole that might have a slight burr to it with a fine file (have used even a fingernail file in the past, aluminum is easy to clean). A new gasket can seal that leak.

There are no dark secrets. Try and reuse, and go from there.

- George

No Dark Secrets! I love that! I also want to call the blow/suck test on the reed valve the "huff and puff" test!
Thank you very much!
Dave

Hi all,
Glad to report that the last piece, the crankshaft has been refurbished. The idea to use an old prop screw and put it in a drill press, applying 2000 grit wet/dry paper (with oil) was a fantastic idea. I double back taped a piece of the paper to a popsicle stick that had been sanded flat. Lightly oiled, the crankshaft slides freely into the crankcase and spins freely. See pic.

Revisit on the reed valve. I took your advice and installed the unworn side toward the sealing surface instead of working the worn side more. That is when I noticed a "crease" in one of the legs of the reed where the leg meets the main circular area. But I believe it is outside the sealing surface. I most likely did the damage as there were multiple clean sessions with trying to clean the reed. I may have gotten too aggressive with the pressure on the Q-Tip and wrinkled the reed at that location. The "blow/suck" test should tell me if it will seal. But, I'd like your advice on whether I should go to the trouble of assembling like this or just switch it out with a mylar reed. See pics. The "wrinkle" is at the lower leg in the direct overhead shot photo and on the right-hand side of the second, angled shot photo. I did check the retainer clip installation. The reed spins freely beneath the clip.

One photo shows a small bench arbor press I picked up years ago at an estate sale with no specific idea what I would use it for. I am thinking of using it to press on the prop drive plate back onto the crank shaft. Of course, the crankshaft would have to be supported up from the base of the press with a stubby wood dowel or perhaps an appropriately sized socket from a socket wrench set. I would protect the drive plate with a small piece of flat wood. Please comment on this approach.

Since I've only been using electric motors in my RC planes, I am also building a little test stand so I can C-clamp the test stand to the park bench where we fly. After I receive feedback on this post. I hope my next post will be a video of the little PeeWee running!

Thanks again for all your help.
Dave

You are making good progress. For the prop drive I usually use the screw to hold the propeller normally it is easy to put back in place but to avoid damaging the threads using a pres is a good way be careful not to install it crooked With experience I can say that using a thermal engine rather than an electric one involves a challenge And personally that's what I prefer, I like the realism and sound that a thermal engine offers compared to the sound of an electric chop vac. If everything is in good condition with a little practice you should be able to start it without problem. and to keep your engine in good condition you will have to mix fuel unless you find a fuel specially formulated for this small engine then yes a nitro engine requires more preparation and more work but I like being able to fill up with fuel and get back in the air faster than charging batteries

The small defect on the valve should not influence the operation too much as long as the valve works well if the suck blow test passed with sucest. and even with a very slight air leak it can still work it just reduce the performance One difficult thing is to build the model or in the case of a conversion to position the motor well because the torque of the motor is different from that of an electric motor and the piloting also slightly different because without throttle control the model will fly at full speed but hey an experienced pilot should not have any difficulty sometimes landing without power is a problem but it all depends on the model and type of plane chosen

Really nice work, @LooseSpinner99 , it is coming right along.

You may already know this, but combustion air-fuel explosions every revolution can cause vibrational fatigue on props. There is rapid acceleration of the prop caused by the piston "jerk" transmitted through the con-rod to the crankshaft to the prop. This accelerates the prop, which then the nertia of the prop and engine moving parts allow it to coast the rest of the revolution until it happens again.

Hence props for internal combustion engines are beefier, especially the hub area to withstand this constant vibration.

Electric props because there is no impulse vibration, are thinner and lighter in profile. These can fail if used on glow engines, throwing blades. A blade flying off at 15,000 RPM can put out an eye.

Some have been experimenting with electric Bullnose props, as these have a heavier duty hub. I bought some to experiment with, as half-A glow props are getting harding to find in the right sizes.

But the court is still out on those. Doesn't hurt to wear some sort of eye protection, even regular glasses with correcting lenses, when messing with engines.

Coming together well Dave….I like to pull the drive plate back on the crankshaft using the prop screw…. Better chance of keeping it straight IMO …. Before you put it back on make sure the splines in the shaft and the plate are clean too…. Use some oil to help it seat well…Let us know how it fires up for you

Even a brand new reed valve might not seal properly when installed. It may require itself to be flipped over. I personally would discard your reed valve. It's already deformed from running hence the circular pattern and it's one leg is deformed. A suck blow test should be performed prior to reassembly unless you enjoy taking your engine apart multiple times. The reed is one of the most important pieces of the puzzle here. If it's not right the engine isn't going to run properly. It might run but it might not peak, it might not start easily or not needle properly.

Good morning to you all,

To davidll1984,
Thanks for your comments. I did purchase a quart of SIG High Performance fuel, 25% nitro. So, as advised earlier, I'll need to use two head gaskets. As I understand it, the SIG fuel uses castor oil and does not mix in any synthetic oil. But I have not spec sheet to prove that. If there is any indication there is a problem with the blow/suck test, I will change out the copper reed for the mylar one.

To GallopingGhostler,
Thank you for the reminder. I was a couple years away from retirement about 10 years ago when I start learning RC flying. My trainers were all electric powered. That seemed to be in the time of transition of popularity from internal combustion engines to brushless electric for small models. At that time, I remember a lot of warnings about mixing electric propellers with the internal combustion engines because of the higher stress on the propellers. But I haven't seen any of that kind of warning/precaution lately. The safety glasses is an excellent idea. When we were kids messing around with Cox 049 U-control planes, nobody seemed concerned and suggested safety glasses. I'll have to find an instruction sheet for those types of U-control planes and see if they mentioned using safety glasses!

To rdw777,
Thank you! I guess I was over thinking how to put the drive plate back on. I had to use a lot of "taps" on the hammer to drive out the crankshaft, but I now realize that was because it was so varnished up. I will definitely use your method for reinstalling the drive plate.

To Ken Cook,
Yes, I was worried about this as well. I definitely plan to do the blow/suck test. If I have any trouble starting or adjusting the engine, that will be the first think I do, change out the reed. After I run this motor, I plan to disassemble, clean and re-assemble it with the light machine oil I'm using. It is going to sit around for a while, while I build the model for it. I could convert the model to electric RC and I do plan to make it two channel RC anyway. But my friend gave me this motor. So, that is why I'm giving this a try. I thought I would tackle the motor first before starting model.

Thanks all for your feedback!

I have a question about throttling. All the throttles I've seen for Pee Wee and Baby Bee Cox engines, throttle/choke off the exhaust. Is there a reason(s) for not choking off the air inlet?

Cheers,
Dave

Hello Dave, this is one of the available "choke" type throttles used with the horseshoe backplates of 049 COX engines. I personally prefer exhaust throttle that allows smoother control and lower, stable idle speed than the choke tubes with which the air-fuel mixture may become too rich when choked, and cause a flame out by overcooling the glow filament in the glow head.

For tanked Bees ACE RC designed a venturi throttle control, and an interesting DIY  post by Roddie is here:

https://www.coxengineforum.com/t5486-049-reed-valve-venturi-throttle?highlight=Tanked+throttle

This is also sold by e.g.  COX International:

https://coxengines.ca/back-end/throttle-for-cox-049-engine-bee-style.html


I also checked by old COX instruction sheets but could not find any advice on the use of eye protection.

On page 4 of this document, however COX recommends the avoidance of plastic propellers except nylon..
https://drive.google.com/file/d/1f7b_D3UFOlfIlGZUKfx931a_OkCXiMRx/view

The plastic propellers of the time must have been too brittle and susceptible to throwing blades.

I have a question about throttling. All the throttles I've seen for Pee Wee and Baby Bee Cox engines, throttle/choke off the exhaust. Is there a reason(s) for not choking off the air inlet?

Cheers,
Dave

balogh wrote:
For tanked Bees ACE RC designed a venturi throttle control, and an interesting DIY  post by Roddie is here:

https://www.coxengineforum.com/t5486-049-reed-valve-venturi-throttle?highlight=Tanked+throttle

Hi Dave, I understand your wanting to throttle an IC/RC aero-engine. It will complicate the build.. if you try to apply the "Ace" design to the PeeWee .020 engine. I'm not sure if it's possible to apply the Ace design to the PeeWee. Being a smaller engine; the venturi-tube/air-intake orifice may be a smaller diameter than the .049/Bee engine's. I should have measured "my" PeeWee when I had it apart recently. The .049/Bee engine's air-intake is .063" which is a perfect fit for a .062" music-wire plunger-needle to work with.

In both; the PeeWee and Bee engines.. the needle/fuel-jet is "right there".. almost immediately inside the venturi where the air comes in. This location is optimal because inserting a tapered-plunger effectively meters the mixture.. rather than choking-off the air. The PeeWee may well have the same size air-intake at the backplate.. but I don't know about the venturi-tube in the tank-bowl.

The Ace design requires the tapered-plunger to pass from inside the nose of the fuse; through the firewall and center of the tank-mount pattern.. so as to align with the engines air-intake. This requires a servo.. and space behind the firewall for the plunger's linkage. ALSO; the Ace design requires the REMOVAL of the little metal mesh screen which covers the air-intake. REMOVING that little mesh screen exposes the venturi to foreign matter which can enter and foul the reed-sealing.. so it's important to provide another means to filter the air.

Ace didn't (AFAIK) design their system for the Cox PeeWee.. and that may be because it wasn't effective.

LooseSpinner99 wrote:To rdw777,
Thank you! I guess I was over thinking how to put the drive plate back on. I had to use a lot of "taps" on the hammer to drive out the crankshaft, but I now realize that was because it was so varnished up. I will definitely use your method for reinstalling the drive plate.

Glad you’re getting some good responses Dave…. This may turn into a referral thread for .020’s …..A little more on the drive plate….I know you’re already past this but maybe for next time…..Taking the plate off is the place to use the press or vice……I use a small vise for this with the crank case protected by a piece of wood….If it seems to offer any too much resistance at all get it hot and it will loosen that varnish and  go much easier..

rdw777 wrote:

LooseSpinner99 wrote:To rdw777,
Thank you! I guess I was over thinking how to put the drive plate back on. I had to use a lot of "taps" on the hammer to drive out the crankshaft, but I now realize that was because it was so varnished up. I will definitely use your method for reinstalling the drive plate.

Glad you’re getting some good responses Dave…. This may turn into a referral thread for .020’s …..A little more on the drive plate….I know you’re already past this but maybe for next time…..Taking the plate off is the place to use the press or vice……I use a small vise for this with the crank case protected by a piece of wood….If it seems to offer any too much resistance at all get it hot and it will loosen that varnish and  go much easier..

You can also use a threaded spinner-hub and stud in the same way..

Good morning to you all,

GREAT feedback thank you!

To: balogh and roddie
I stand corrected, I have seen these inlet choke type throttles before on the Cox International Engine website, but I obviously have no experience with them.
The article on the needle throttle at the engine inlet by ACE was very, very interesting! This is something to experiment with later, definitely. This is where I confess that i am having a lot of fun and learning a lot refurbishing this first motor. So, I recently picked up another used Pee Wee on Ebay that came with some misc. extra parts. Both the current motor I'm working on and this second one I've obtained both have intact air inlet screens. I think it would be borderline sacrilegious to remove a completely perfect inlet screen! But one of the misc. parts that came with the second motor was a backplate that otherwise looks to be in good condition. The air inlet screen on this backplate is damaged. So, this might be the candidate backplate I use to try making an air inlet throttle with. I watched roddie's video. That was really great, and I copied off the directions so I can study them. I agree, some kind of other screen/filter at the air inlet would be recommended. It would have to fit at the bottom of the fuel tank to firewall where the air inlet starts. Got to think about that.


To: rdw777
Awesome pics of driving out the crankshaft with the vice! A much more elegant method than tapping it out with a hammer! Especially since I could hold the heat gun in one hand and apply light pressure with the vice!
Thank you for sharing that!

Cheers,
Dave

LooseSpinner99 wrote:  I watched roddie's video.  That was really great, and I copied off the directions so I can study them.  I agree, some kind of other screen/filter at the air inlet would be recommended.  It would have to fit at the bottom of the fuel tank to firewall where the air inlet starts.  Got to think about that.

Hi Dave, I'm happy that you enjoyed my video on the Ace-style venturi-throttle.

In the case that you have a backplate without the little screen; you can use the filter media available for air-conditioners (in-window type). One package would last you and all your modeling friends a lifetime. You can find it in the hardware dept. of most department-stores or home-improvement centers.






The filter media is spongy.. and will squash-flat when the engine is mounted to a firewall. What's more; the Ace-style plunger-needle will simply pass-through it without issue. I have not found it to restrict the airflow to any measurable degree. You can also use this filter media for its shock-absorbing/dampening properties as in wrapping a radio receiver with it. I've often used it in-between an external fuel-tank and where it contacts a solid surface to dampen vibrations that could cause fuel-foaming.




This red "Killer Bee" High-Performance backplate which uses an external fuel-cell is NOT supplied with a screen; therefore I have opted to use the filter media for that application.

Roddie
Interestingly I have also added screens to several of my KB  backplates, cut from a stainless steel mesh and fixed with a small O ring wound around both ends of the spraybar.



Not tailored to ultimate precision,  but works well with no apparent impact on rpm

balogh wrote:Roddie
Interestingly I have also added screens to several of my KB  backplates, cut from a stainless steel mesh and fixed with a small O ring wound around both ends of the spraybar.



Not tailored to ultimate precision,  but works well with no apparent impact on rpm

I LIKE IT!!!

The Polyurethane filter media that I use will eventually degrade/break-down with exposure to the elements in the glow-fuel.. but most of us generally remove the engine(s) from a model at the close of a flying season for maintenance/inspection. The filter media can be accessed/discarded at that time.

Hi Roddie,

Wow, this is really great information! And great pics and work. I'll look for that insulation material next time I'm at the hardware store!
Thank you for sharing. Would you be willing to share the source of your stainless-steel wire mesh?

Dave

Dave,

The stainless steel woven wire mesh is from a hardware store in Budapest, Hungary, where I live, but I guess you will find the same or similar in the US...I think this is used to filter paint materials so you can inquire in paint shops, too.
The steel wire is 0.19mm thick and the mesh size is 0.08mm. I trust it helps.

Andras aka balogh

Good morning balogh,

First let me sincerely apologize. I missed the part in the conversation where the author went from Roddie to you. Thank you for the info on the wire mesh!
Budapest, Hungary! That is great. The internet makes the world smaller and all of us closer. Hopefully someday that might help us all.

Yes, your info helped a lot. I will check the local hardware stores here to see what they have.

Using your info, I also looked at an industrial supply company called McMaster-Carr. The had lots of different types of wire mesh. For example, I found the following:
McMaster Carr P/N: 9319T176
316 stainless steel
mesh size 60 x 60
wire diameter: .19mm (.0075")
mesh opening: .23mm (.009")
1 ft x 1 ft sq price was about $10 US dollars.

McMaster Carr P/N: 9319T185 (this one is close to what you quoted)
316 stainless steel
mesh size 150 x 150
wire diameter: .066mm (.0026")
mesh opening: .104mm (.0041")
1 ft x 1 ft sq price was about $6 US dollars.

And there was a whole lot more selections and even finer mesh opening sizes!

The issue with McMaster Care is they are primarily a U.S. business-to-business operation and claim they do not sell to private persons. They do ship internationally. But because they assume you are a business; time is money, and they can get your order to you in a day or two. So, shipping cost is pricy. The few items I've ordered, I spent more on shipping cost than the item I was buying. But I could not find it anywhere else. Also, small items come in large lots, i.e. 50, or 100 fasteners can be a minimum order quantity when maybe you only need 8 or 10!

If any of you are not familiar with McMaster Carr, there is a small write up on Wikipedia about them. How I was able to get an "account": When I was working, I just used my company name in the account info, and they opened an account for me. I wasn't ordering for the company. I was ordering for me! Even though I am retired I seem to still be able to order from them since my account has been established. It is rare that I order something. It has to be really unique. The last order was for special fasteners and standoff spacers for a RC transmitter tray I made from scratch. That was about 3 years ago.

I hope this helps!

PS
I installed the propeller drive plate onto the crankshaft yesterday. All went well and the propeller/crankshaft spins smoothly and for a long time!

Cheers Dave

Hi All,
I hope I haven’t said anything to offend anyone. The thread has been kind of quiet. My only comments going forward will stay on subject.

Final assembly starts today, hopefully finished. I’m soaking thread and cotton in castor oil right now. If all goes well, on to the leak test.

That’s all for now.
Dave

Hello Dave, The pace of CEF is not always that speedy and sometimes days may pass before someone reacts to a post..I assume the election may also have distracted the attention if some of you guys in the US..

McMaster is interestingly present in Hungary as well, a small hardware store under that name runs in my neighborhood, but they may just abuse the brand, I am not sure.

I do not recall how I selected the steel woven mash when I bought it...I just wanted something similar in appearance to the screens on COX engines, I mean not too dense so that excessive pressure drop of air is avoided, but dense enough to filter airborne particles.

The one I finally bought seems good enough not to impair the engine speed.